JP4112158B2

JP4112158B2 - Thermoelectric material manufacturing method, thermoelectric material, and thermoelectric material manufacturing apparatus

Info

Publication number: JP4112158B2
Application number: JP2000201198A
Authority: JP
Inventors: 康雄中原; 和彦高橋; 幸宏磯田
Original assignee: National Institute for Materials Science; Sanyo Electric Co Ltd
Current assignee: National Institute for Materials Science; Sanyo Electric Co Ltd
Priority date: 2000-07-03
Filing date: 2000-07-03
Publication date: 2008-07-02
Anticipated expiration: 2020-07-03
Also published as: JP2002026403A

Description

【０００１】
【発明の属する技術分野】
本発明は、熱電材料の製造方法、熱電材料及び熱電材料製造装置であって、特に、原料融液を冷却して熱電材料を製造する熱電材料の製造方法、Ｂｉ、Ｓｂ、Ａｇ、Ｐｂ、Ｇｅ、Ｃｕ、Ｓｎ、Ａｓ、Ｓｅ、Ｔｅ、Ｆｅ、Ｍｎ、Ｃｏ、Ｓｉから選択される少なくとも２種類以上の元素を含む原料から製造される熱電材料及び原料融液を冷却して熱電材料を製造する熱電材料製造装置に関する。
【０００２】
【従来の技術】
従来、この種の熱電材料では、熱電材料の性能を表す性能指数Ｚが次式のように定義されている。
【０００３】
【数１】
Ｚ＝σ＊α²／κ
この式において、σは電気伝導率、αはゼーベック係数、κは熱伝導率である。熱伝導率κは、物質を構成する原子核自体の振動によるもの（フォノン熱伝導率）と、キャリア（電子又はホール）の移動によるもの（キャリア熱伝導率）との和で与えられる。
【０００４】
性能指数Ｚが大きい熱電材料を得るために、様々な製造方法が提案されている。特に、熱伝導率κを小さくする方法として、溶融状態の原料を急冷し、極微結晶またはアモルファス状態にする方法が提案されている（例えば、特開平８−１１１５４６号公報、特開平５−３３５６２８号公報など）。
【０００５】
【発明が解決しようとする課題】
しかしながら、溶融状態から急冷する方法では、急冷して得られた材料を機械的に粉砕して得られた粉末を焼結してバルク状にする必要がある。この場合、粉砕する際に不純物が混入する場合がある。
【０００６】
本発明の熱電材料の製造方法は、不純物の混入が少なく性能指数の高い熱電材料を製造することを目的の一つとする。また、本発明の熱電材料は、不純物の混入量が低く、性能指数が高い材料であることを目的の一つとする。また、本発明の熱電材料製造装置は、不純物の混入が少なく性能指数が高い熱電材料を製造できる装置であることを目的の一つとする。
【０００７】
【課題を解決するための手段】
本発明の熱電材料の製造方法は、原料融液を冷却して熱電材料を製造する熱電材料の製造方法であって、前記融液を冷却台表面に薄膜状に広げ、該冷却台で冷却して第一熱電材料層を形成する第一熱電材料層形成工程と、該第一熱電材料層上へ前記融液を薄膜状に広げ、前記第一熱電材料層を介して前記冷却台で冷却して、前記第一熱電材料層上に第二熱電材料層を形成する第二熱電材料層形成工程と、を備え、前記第一熱電材料層形成工程は、滴下した前記融液を対向配置され各々駆動可能な二つの冷却台で挟持し、前記融液を前記冷却台の少なくとも一方の表面に薄膜状に広げ冷却した後、前記二つの冷却台を離し、前記第一熱電材料層を形成する工程であり、前記第二熱電材料層形成工程は、滴下した前記融液を前記二つの冷却台で挟持し、前記融液を前記冷却台の少なくとも一方の表面に形成された前記第一熱電材料層上に薄膜状に広げ冷却した後、前記二つの冷却台を離し、前記第二熱電材料層を形成する工程であり、少なくとも二層の積層された熱電材料層を有する熱電材料を製造することを特徴とする。なお、各熱電材料層は二つの冷却台の一方のみに形成されるものとすることもできるが、二つの冷却台に各々形成されるものとすることもできる。
【０００８】
本発明の熱電材料の製造方法では、第一熱電材料層と第二熱電材料層との少なくとも二層の熱電材料層が積層された熱電材を冷却台表面に形成することができる。その結果、焼結してバルク状にする必要がなく、熱電材料への不純物の混入を抑えることができる。
【０００９】
この本発明の参考形態の熱電材料の製造方法において、前記冷却台は、表面が略円形で回転可能な台であり、前記第一熱電材料層形成工程は、回転する前記冷却台表面に前記融液を滴下し、該融液を前記冷却台表面の半径方向に薄膜状に広げ前記第一熱電材料層を形成する工程であり、前記第二熱電材料層形成工程は、回転する前記冷却台表面に形成された前記第一熱電材料層上に前記融液を滴下し、前記融液を前記半径方向に薄膜状に広げ前記第二熱電材料層を形成する工程であるものとすることもできる。冷却台を回転させることによって、冷却台表面に均一に融液を広げることができ、各熱電材料層の層の厚さを冷却台表面に渡って均一にすることができる。その結果、均一な厚さの熱電材料を製造することができる。
【００１１】
この本発明の参考形態の熱電材料の製造方法において、前記冷却台は、該冷却台の表面温度を調整する温度調整手段が設けられているものとすることもできる。冷却台の表面温度を調整することで、熱電材料層が多数積層されても、融液を最適な温度で冷却することができる。
【００１２】
本発明の参考形態の熱電材料は、Ｂｉ、Ｓｂ、Ａｇ、Ｐｂ、Ｇｅ、Ｃｕ、Ｓｎ、Ａｓ、Ｓｅ、Ｔｅ、Ｆｅ、Ｍｎ、Ｃｏ、Ｓｉから選択される少なくとも２種類以上の元素を含む原料から製造される熱電材料であって、前記原料からなり積層された複数の熱電材料層を備え、前記各熱電材料層は、該各熱電材料層の積層方向に伸びる柱状結晶粒を有することを特徴とする。
【００１３】
本発明の参考形態の熱電材料では、各熱電材料層が積層されており、各熱電材料層はその積層方向に伸びる柱状結晶粒を有するため、熱伝導率が低くなる。また、積層方向の強度も高くなる。
【００１４】
この本発明の参考形態の熱電材料において、平均結晶粒径が１〜５μｍであり、充填率が９８％〜１００％であるものとすることもできる。本発明の熱電材料は、熱電材料の粉末を焼結してバルク状にして製造した熱電材料と比較して、平均結晶粒径が小さくなるため、結晶粒界によるフォノン散乱が増大し、熱伝導率を低減することができる。また、充填率が高いため電気伝導率は大きく保たれる。以上の結果、性能指数の高い材料となる。
【００１５】
本発明の熱電材料製造装置は、原料融液を冷却して熱電材料を製造する熱電材料製造装置であって、対向配置され前記融液を表面に薄膜状に広げ冷却する二つの冷却台と、前記二つの冷却台をその対向間隔を遠近させる前記二つの冷却台の駆動手段と、前記二つの冷却台の間に前記融液を供給する融液供給手段と、を備え、前記駆動手段は、前記融液供給手段により供給された前記融液を挟持する間隔と、次いで前記融液が前記二つの冷却台の間で薄膜状に広げられ冷却されて第一熱電材料層が形成された後、前記二つの冷却台を離れさせた間隔を持つように駆動し、前記二つの冷却台の表面と前記第一熱電材料層との密着力に応じて、少なくとも一方の冷却台の表面に第一熱電材料層を形成させるように駆動するものであり、さらに、前記駆動手段は、前記融液供給手段により供給された前記融液を挟持するように前記二つの冷却台の対向間隔を縮める方向に駆動し、次いで少なくとも一方の冷却台の表面に第一熱電材料層が形成されている前記二つの冷却台の間に前記融液が薄膜状に広げられ冷却されて第二熱電材料層が形成された後、前記二つの冷却台の間隔を広げる方向に駆動し、前記二つの冷却台の少なくとも一方の表面に形成された第一熱電材料層上に第二熱電材料層を形成させるように駆動するものであり、前記冷却台表面に少なくとも二層の積層された熱電材料層を有する熱電材料を製造することを特徴とする。なお、各熱電材料層は二つの冷却台の一方のみに形成することもできるが、二つの冷却台に各々形成することもできる。
【００１６】
本発明の熱電材料製造装置では、複数の熱電材料層が積層された熱電材料を冷却台表面に形成することができる。その結果、焼結してバルク状にする必要がなく、熱電材料への不純物の混入を防ぐことができる。
【００１７】
この本発明の参考形態の熱電材料製造装置において、熱電材料製造装置は、前記冷却台を回転させる冷却台回転手段を備え、前記冷却台は、その表面が略円形であり前記冷却台回転手段により回転するとともに前記融液供給手段により供給された前記融液を前記表面の半径方向に薄膜状に広げ前記熱電材料層を形成するものとすることもできる。冷却台を回転させることによって、冷却台表面に均一に融液を広げることができ、各熱電材料層の層の厚さを冷却台表面に渡って均一にすることができる。その結果、均一な厚さの熱電材料を製造することができる。
【００１９】
この本発明の参考形態の熱電材料製造装置において、前記冷却台は、該冷却台の表面温度を調整する温度調整手段が設けられているものとすることもできる。冷却台の表面温度を調整することで、熱電材料層が多数積層されても、融液を最適な温度で冷却することができる。
【００２０】
【発明の実施の形態】
以下、本発明の実施の形態（以下実施形態という）を、図面に従って説明する。なお、各図において同一又は同等の構成要件は、同一の符号を施している。
【００２１】
図１は本参考実施形態の熱電材料製造装置１００の構成を示した概略図である。熱電材料製造装置１００は、周囲を高周波加熱用コイル１０で巻かれ先端にノズル１２を備える加熱容器１４と、温度制御された循環水によって水冷され一定の温度に保たれ表面がＢｉＴｅ合金融液と濡れ性を持った材料で被覆された水冷金属円盤１６とを真空漕１８内に備える。真空漕１８外には、水冷金属円盤１６と機械的に接続されるモータ２０を備えており、モータ２０は水冷金属円盤１６を所定の回転数で回転させる。
【００２２】
加熱容器１４は、石英を材料としノズル１２と一体成型されており、内部にＢｉの粉末粒子とＴｅの粉末粒子との混合物が入れられている。高周波加熱用コイル１０は、加熱容器１４内部の混合物を加熱し溶融させＢｉＴｅ合金融液を形成する。加熱容器１４内には、図示していないが、ＢｉＴｅ合金融液の温度を測定する石英やアルミナ等の耐火物でシースされた熱電対が設けられており、ＢｉＴｅ合金融液の温度に応じて高周波加熱用コイル１０に流れる電流を制御し、ＢｉＴｅ合金融液の温度が所望の温度になるように制御する。加熱容器１４内には、図示していない不活性ガス供給系からＡｒガスなどの不活性ガスが供給される。加熱容器１４は、内部の不活性ガスの圧力を上げることで、ＢｉＴｅ合金融液をノズル１２から水冷金属円盤１６へ滴下する。この滴下速度及び滴下量は、不活性ガスの圧力を制御することで、適宜変えることができる。ノズル１２から真空漕１８内に漏れ出た不活性ガスは、図示しない真空ポンプで排気され、真空漕１８内の気圧をある一定値以下、例えば１．３３×１０^-3［Ｐａ］（１０^-5［Ｔｏｒｒ］）以下に保つことができる。
【００２３】
次に、熱電材料製造装置１００を用いて熱電材料を製造する方法を説明する。図２は、熱電材料の製造工程を示した図である。最初に、Ｂｉの粉末粒子とＴｅの粉末粒子を混合し真空または不活性雰囲気中で加熱容器１４に入れる（工程Ｓ１０）。次に、高周波加熱用コイル１０を通電し、混合物を加熱溶融させＢｉＴｅ合金融液を形成する（工程Ｓ１２）。
【００２４】
そして、水冷金属円盤１６をモータ２０で回転させ、回転する水冷金属円盤１６の表面にノズル１２からＢｉＴｅ合金融液を滴下する（工程Ｓ１４）。滴下されたＢｉＴｅ合金融液２２は、回転する水冷金属円盤１６による遠心力で水冷金属円盤１６の半径方向（図１における矢印ａ方向）へ薄膜状に広がり、水冷金属円盤１６で冷却され凝固し、図３に示す熱電材料層３０となる。熱電材料層３０は、水冷金属円盤１６に冷却されるため、水冷金属円盤１６表面に対して垂直な方向に伸びる柱状の結晶粒の集合体となる。
【００２５】
次に、図示していない制御装置でＢｉＴｅ合金融液が所定量滴下したか否かを判定する（工程Ｓ１６）。所定量滴下されていなければ、熱電材料層３０上にノズル１２からＢｉＴｅ合金融液を滴下する（工程Ｓ１４）。熱電材料層３０上に滴下されたＢｉＴｅ合金融液は熱電材料層３０上で薄膜状に広がり、熱電材料層３０を介して水冷金属円盤１６に冷却され凝固し熱電材料層３２となる。その後、滴下量が所定量に達するまで、工程Ｓ１４が繰り返して実行される。工程Ｓ１４を１回行なう度に熱電材料層が一層形成される。
【００２６】
図４は、このように製造された熱電材料の断面図が示されている。水冷金属円盤１６表面には、熱電材料層３０，熱電材料層３２，熱電材料層３４，熱電材料層３６が形成されている。各熱電材料層は、工程Ｓ１４を一回行なうごとに一層ずつ形成される。各熱電材料層は、水冷金属円盤１６表面に対して垂直な方向、即ち、各熱電材料層が積層される方向に伸びる柱状の結晶粒の集合体となっているので、熱伝導率κが低くなり、積層方向の強度も高くなる。また、各熱電材料層は、ＢｉＴｅ合金融液を冷却して直接製造されるので、冷却したのち粉砕し焼結させる方法で製造した熱電材料に比較して、不純物の混入が少ない熱電材料となる。また、平均結晶粒径は１〜５μｍであり、充填率は９８％〜１００％となる。この熱電材料では、平均結晶粒径が小さいため結晶粒界によるフォノン散乱が増大し熱伝導率κが低減される。また、充填率が高いため電気伝導率σが高く保たれる。
【００２７】
水冷金属円盤１６の表面に熱電材料層を積層させ熱電材料を形成した後、水冷金属円盤１６の表面を切り離し、熱電材料を切り出す（工程Ｓ１８）。このように熱電材料を切り出す際に、水冷金属円盤１６とともに切り出すことで、後の素子化工程で必要な熱電材料への電極形成の必要がなくなる。従って、工程数を減らすことができる。
【００２８】
本参考実施形態の熱電材料製造装置１００では、ＢｉＴｅ合金融液を回転する水冷金属円盤１６上に滴下し冷却することを繰り返して積層構造を備える熱電材料を製造したが、他の製造装置で積層構造を備える熱電材料を製造することもできる。
【００２９】
図５は、本実施形態の熱電材料製造装置２００の構成の概略図である。熱電材料製造装置２００は、熱電材料製造装置１００の水冷金属円盤１６に替えて、図面に向かい右側に設けられた駆動軸５０によって真空漕１８の中心部に並行移動可能であり温度制御された循環水によって水冷され一定の温度に保たれ表面がＢｉＴｅ合金融液と濡れ性を持った材料で被覆された冷却台５４と、図面に向かい左側に設けられた駆動軸５２によって真空漕１８の中心部に並行移動可能であり温度制御された循環水によって水冷され一定の温度に保たれ表面がＢｉＴｅ合金融液と濡れ性を持った材料で被覆された冷却台５６とが対向配置されており、ノズル１２から滴下されるＢｉＴｅ合金融液２２の落下位置を検出できる光学式センサ５８を備えている。
【００３０】
熱電材料製造装置２００では、左右の冷却台５４と冷却台５６とが離れた状態で、ノズル１２からＢｉＴｅ合金融液２２を冷却台５４と冷却台５６との間に滴下する。光学式センサ５８でＢｉＴｅ合金融液２２が検出されると、冷却台５４と冷却台５６とが移動し、滴下したＢｉＴｅ合金融液２２を挟持する。ＢｉＴｅ合金融液２２は、冷却台５４と冷却台５６との間で薄膜状に広がり凝固する。ＢｉＴｅ合金融液２２が凝固したら冷却台５４と冷却台５６とを離すが、このとき、ＢｉＴｅ合金融液２２と冷却台５４及び冷却台５６との表面の密着力に応じて、少なくとも冷却台５４及び冷却台５６のいずれかに熱電材料層が付着する。即ち、熱電材料層と冷却台５４表面との密着力が冷却台５６表面との密着力と比較して非常に大きければ冷却台５４に熱電材料層が付着し、熱電材料層と冷却台５４表面との密着力が冷却台５６表面との密着力と比較して非常に小さければ冷却台５６に熱電材料層が付着し、熱電材料層と冷却台５４表面との密着力が冷却台５６表面との密着力と同程度であれば、冷却台５４と冷却台５６との双方に熱電材料層が付着する。
【００３１】
冷却台５４と冷却台５６とを離した後、ノズル１２からＢｉＴｅ合金融液２２を冷却台５４と冷却台５６との間に滴下する。冷却台５４と冷却台５６とは、再び移動し滴下したＢｉＴｅ合金融液２２を挟持し、ＢｉＴｅ合金融液を先に付着した熱電材料層上に付着させる。このように、ＢｉＴｅ合金融液の滴下と熱電材料層上への付着とを繰り返し、図４に示した積層構造を有する熱電材料を製造する。
【００３２】
このように熱電材料製造装置２００においても、積層構造を備える熱電材料を製造することができる。
【００３３】
各実施形態の熱電材料は、ＢｉとＴｅとを原料としたが、それ以外に、Ｓｂ、Ａｇ、Ｐｂ、Ｇｅ、Ｃｕ、Ｓｎ、Ａｓ、Ｓｅ、Ｆｅ、Ｍｎ、Ｃｏ、Ｓｉから選択される元素を少なくとも２種類以上を含むものとすることもできる。特にＢｉ、Ｓｂ、Ａｇ、Ｐｂ、Ｇｅ、Ｃｕ、Ｓｎ、Ａｓの少なくとも１種類とＳｅ又はＴｅとの組み合わせのカルコゲナイト系原料や、Ｆｅ、Ｍｎ、Ｃｏ、Ｇｅのいずれか１種類とＳｉとの組み合わせのシリサイド系原料や、ＢｉＳｂ系原料が好適である。
【００３４】
【発明の効果】
以上説明したように、本発明の熱電材料の製造方法及び熱電材料の製造装置では、第一熱電材料層と第二熱電材料層との少なくとも二層の熱電材料層が積層された熱電材を冷却台表面に形成することができる。その結果、焼結してバルク状にする必要がなく、熱電材料への不純物の混入を抑えることができる。また、本発明の熱電材料では、各熱電材料層が積層されており、各熱電材料層はその積層方向に伸びる柱状結晶粒を有するため、熱伝導率κが低くなり、性能指数の高い熱電材料を製造することができる。
【図面の簡単な説明】
【図１】本参考実施形態の熱電材料製造装置１００の構成を示した概略図である。
【図２】本参考実施形態の熱電材料の製造工程を示す図である。
【図３】本参考実施形態の熱電材料の製造工程途中での断面図である。
【図４】本実施形態の熱電材料の断面図である。
【図５】本実施形態の熱電材料製造装置２００の構成を示した概略図である。
【符号の説明】
１０高周波加熱用コイル、１２ノズル、１４加熱容器、１６水冷金属円盤、２２ＢｉＴｅ合金融液、３０，３２，３４，３６熱電材料層、５４，５６冷却台。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermoelectric material manufacturing method, a thermoelectric material, and a thermoelectric material manufacturing apparatus, in particular, a thermoelectric material manufacturing method for cooling a raw material melt to manufacture a thermoelectric material, Bi, Sb, Ag, Pb, Ge. , Cu, Sn, As, Se, Te, Fe, Mn, Co, Si are produced by cooling a thermoelectric material and a raw material melt produced from a raw material containing at least two elements selected from Si, Te and Te. The present invention relates to a thermoelectric material manufacturing apparatus.
[0002]
[Prior art]
Conventionally, in this type of thermoelectric material, a figure of merit Z representing the performance of the thermoelectric material is defined as follows.
[0003]
[Expression 1]
Z = σ * α ² / κ
In this equation, σ is electrical conductivity, α is Seebeck coefficient, and κ is thermal conductivity. The thermal conductivity κ is given by the sum of the one caused by vibrations of the nuclei themselves constituting the substance (phonon thermal conductivity) and the one caused by the movement of carriers (electrons or holes) (carrier thermal conductivity).
[0004]
In order to obtain a thermoelectric material having a large figure of merit Z, various manufacturing methods have been proposed. In particular, as a method of reducing the thermal conductivity κ, methods of rapidly cooling a raw material in a molten state to form a microcrystalline or amorphous state have been proposed (for example, JP-A-8-111546 and JP-A-5-335628). Gazette).
[0005]
[Problems to be solved by the invention]
However, in the method of quenching from the molten state, it is necessary to sinter powder obtained by mechanically grinding the material obtained by quenching into a bulk form. In this case, impurities may be mixed during pulverization.
[0006]
One object of the method for producing a thermoelectric material of the present invention is to produce a thermoelectric material having a low figure of impurities and a high figure of merit. Another object of the thermoelectric material of the present invention is a material having a low amount of impurities and a high figure of merit. It is another object of the thermoelectric material manufacturing apparatus of the present invention to be an apparatus that can manufacture a thermoelectric material with a low figure of impurities and a high performance index.
[0007]
[Means for Solving the Problems]
The method for producing a thermoelectric material of the present invention is a method for producing a thermoelectric material by cooling a raw material melt, spreading the melt in the form of a thin film on the surface of a cooling table, and cooling it with the cooling table. A first thermoelectric material layer forming step for forming the first thermoelectric material layer, and spreading the melt on the first thermoelectric material layer in a thin film shape, and cooling the first thermoelectric material layer through the first thermoelectric material layer with the cooling table. And a second thermoelectric material layer forming step for forming a second thermoelectric material layer on the first thermoelectric material layer , wherein the first thermoelectric material layer forming step is arranged so that the dropped melt is opposed to each other. Step of sandwiching between two drivable cooling tables, spreading and cooling the melt on at least one surface of the cooling table in a thin film, and then separating the two cooling tables to form the first thermoelectric material layer In the second thermoelectric material layer forming step, the dropped melt is sandwiched between the two cooling stands. The melt is spread in a thin film on the first thermoelectric material layer formed on at least one surface of the cooling table and cooled, and then the two cooling tables are separated to form the second thermoelectric material layer. And producing a thermoelectric material having at least two laminated thermoelectric material layers. Each thermoelectric material layer can be formed on only one of the two cooling tables, but can also be formed on each of the two cooling tables.
[0008]
In the method for producing a thermoelectric material of the present invention, a thermoelectric material in which at least two thermoelectric material layers of a first thermoelectric material layer and a second thermoelectric material layer are laminated can be formed on the surface of the cooling table. As a result, it is not necessary to sinter into a bulk shape, and contamination of impurities into the thermoelectric material can be suppressed.
[0009]
The method of manufacturing a thermoelectric material reference embodiment of the present invention, the cooling block, the surface is rotatable platform in a substantially circular shape, said first thermoelectric material layer forming step, the fusion in the cooling stage the surface of the rotating Dropping the liquid and spreading the melt into a thin film in the radial direction of the surface of the cooling table to form the first thermoelectric material layer, wherein the second thermoelectric material layer forming step includes rotating the surface of the cooling table The melt may be dropped on the first thermoelectric material layer formed in the step, and the melt may be spread in a thin film shape in the radial direction to form the second thermoelectric material layer. By rotating the cooling table, the melt can be spread uniformly on the surface of the cooling table, and the thickness of each thermoelectric material layer can be made uniform over the surface of the cooling table. As a result, a thermoelectric material having a uniform thickness can be manufactured.
[0011]
In the method for manufacturing a thermoelectric material according to the reference embodiment of the present invention, the cooling table may be provided with temperature adjusting means for adjusting the surface temperature of the cooling table. By adjusting the surface temperature of the cooling table, the melt can be cooled at an optimum temperature even when a large number of thermoelectric material layers are stacked.
[0012]
The thermoelectric material of the reference form of the present invention is a raw material containing at least two kinds of elements selected from Bi, Sb, Ag, Pb, Ge, Cu, Sn, As, Se, Te, Fe, Mn, Co, and Si. A thermoelectric material manufactured from the above, comprising a plurality of thermoelectric material layers stacked from the raw material, each thermoelectric material layer having columnar crystal grains extending in the stacking direction of each thermoelectric material layer And
[0013]
In the thermoelectric material of the reference form of the present invention, each thermoelectric material layer is laminated, and each thermoelectric material layer has columnar crystal grains extending in the laminating direction, so that the thermal conductivity is lowered. Moreover, the strength in the stacking direction is also increased.
[0014]
In the thermoelectric material of the reference form of the present invention, the average crystal grain size may be 1 to 5 μm, and the filling rate may be 98% to 100%. The thermoelectric material of the present invention has a smaller average crystal grain size than a thermoelectric material produced by sintering a thermoelectric material powder into a bulk form, and thus increases phonon scattering due to grain boundaries, and heat conduction. The rate can be reduced. Moreover, since the filling rate is high, the electrical conductivity is kept large. As a result, the material has a high performance index.
[0015]
The thermoelectric material manufacturing apparatus of the present invention is a thermoelectric material manufacturing apparatus that manufactures a thermoelectric material by cooling a raw material melt, two cooling stands that are arranged opposite to each other and spread and cool the melt on the surface, Driving means for the two cooling stands for moving the two cooling stands closer to each other, and a melt supply means for supplying the melt between the two cooling stands , the driving means comprising: After the interval between which the melt supplied by the melt supply means is sandwiched, and then the melt is spread in a thin film between the two cooling stands and cooled to form the first thermoelectric material layer, The two cooling tables are driven so as to be spaced apart from each other, and the first thermoelectric power is applied to the surface of at least one cooling table in accordance with the adhesion between the surfaces of the two cooling tables and the first thermoelectric material layer. Driving to form a material layer, and The moving means is driven in a direction to reduce the facing distance between the two cooling stands so as to sandwich the melt supplied by the melt supplying means, and then the first thermoelectric material layer is formed on the surface of at least one of the cooling stands. After the melt is spread in a thin film between the two cooling stands formed and cooled to form a second thermoelectric material layer, it is driven in a direction to widen the interval between the two cooling stands, The second thermoelectric material layer is driven to be formed on the first thermoelectric material layer formed on at least one surface of the two cooling tables, and at least two thermoelectric layers laminated on the cooling table surface. A thermoelectric material having a material layer is manufactured. Each thermoelectric material layer can be formed on only one of the two cooling tables, but can also be formed on each of the two cooling tables.
[0016]
In the thermoelectric material manufacturing apparatus of the present invention, a thermoelectric material in which a plurality of thermoelectric material layers are stacked can be formed on the surface of the cooling table. As a result, it is not necessary to sinter and form a bulk, and contamination of impurities into the thermoelectric material can be prevented.
[0017]
In the thermoelectric material manufacturing apparatus according to the reference embodiment of the present invention, the thermoelectric material manufacturing apparatus includes cooling table rotating means for rotating the cooling table, and the cooling table has a substantially circular surface and is provided by the cooling table rotating means. The thermoelectric material layer may be formed while rotating and spreading the melt supplied by the melt supply means in a thin film shape in the radial direction of the surface. By rotating the cooling table, the melt can be spread uniformly on the surface of the cooling table, and the thickness of each thermoelectric material layer can be made uniform over the surface of the cooling table. As a result, a thermoelectric material having a uniform thickness can be manufactured.
[0019]
In the thermoelectric material manufacturing apparatus reference embodiment of the present invention, the cooling stage can be assumed that the temperature adjusting means for adjusting the cooling stage of the surface temperature is provided. By adjusting the surface temperature of the cooling table, the melt can be cooled at an optimum temperature even when a large number of thermoelectric material layers are stacked.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. In each figure, the same or equivalent constituent elements are given the same reference numerals.
[0021]
Figure 1 is a schematic diagram showing the structure of a thermoelectric material manufacturing apparatus 100 of the present reference embodiment. The thermoelectric material manufacturing apparatus 100 includes a heating container 14 that is wound around by a high frequency heating coil 10 and has a nozzle 12 at the tip, and is cooled with water by temperature-controlled circulating water and maintained at a constant temperature. A water-cooled metal disk 16 coated with a material having wettability is provided in a vacuum bowl 18. A motor 20 that is mechanically connected to the water-cooled metal disk 16 is provided outside the vacuum trough 18, and the motor 20 rotates the water-cooled metal disk 16 at a predetermined number of rotations.
[0022]
The heating container 14 is made of quartz as a material and is integrally formed with the nozzle 12, and a mixture of Bi powder particles and Te powder particles is placed therein. The high-frequency heating coil 10 heats and melts the mixture in the heating container 14 to form a BiTe financial solution. Although not shown in the figure, a thermocouple sheathed with a refractory material such as quartz or alumina is provided in the heating container 14 to measure the temperature of the BiTe combined financial liquid. Depending on the temperature of the BiTe combined financial liquid, The current flowing through the high-frequency heating coil 10 is controlled so that the temperature of the BiTe financial solution becomes a desired temperature. An inert gas such as Ar gas is supplied into the heating container 14 from an inert gas supply system (not shown). The heating container 14 drops the BiTe combined financial liquid from the nozzle 12 onto the water-cooled metal disk 16 by increasing the pressure of the internal inert gas. The dropping speed and dropping amount can be changed as appropriate by controlling the pressure of the inert gas. The inert gas leaking from the nozzle 12 into the vacuum chamber 18 is exhausted by a vacuum pump (not shown), and the atmospheric pressure in the vacuum chamber 18 is below a certain value, for example, 1.33 × 10 ⁻³ [Pa] (10 ^{− 5} [Torr]) or less.
[0023]
Next, a method for manufacturing a thermoelectric material using the thermoelectric material manufacturing apparatus 100 will be described. FIG. 2 is a diagram showing a manufacturing process of a thermoelectric material. First, powder particles of Bi and powder particles of Te are mixed and put in the heating container 14 in a vacuum or an inert atmosphere (step S10). Next, the high frequency heating coil 10 is energized, and the mixture is heated and melted to form a BiTe combined financial liquid (step S12).
[0024]
Then, the water-cooled metal disk 16 is rotated by the motor 20, and BiTe combined financial liquid is dropped from the nozzle 12 onto the surface of the rotating water-cooled metal disk 16 (step S14). The dropped BiTe financial liquid 22 spreads in a thin film shape in the radial direction of the water-cooled metal disk 16 (in the direction of arrow a in FIG. 1) by the centrifugal force of the rotating water-cooled metal disk 16, and is cooled and solidified by the water-cooled metal disk 16. The thermoelectric material layer 30 shown in FIG. Since the thermoelectric material layer 30 is cooled by the water-cooled metal disk 16, it becomes an aggregate of columnar crystal grains extending in a direction perpendicular to the surface of the water-cooled metal disk 16.
[0025]
Next, it is determined whether a predetermined amount of BiTe combined financial liquid has been dropped by a control device (not shown) (step S16). If the predetermined amount is not dripped, BiTe combined financial liquid is dripped from the nozzle 12 on the thermoelectric material layer 30 (process S14). The BiTe combined financial liquid dropped on the thermoelectric material layer 30 spreads in a thin film shape on the thermoelectric material layer 30, is cooled by the water-cooled metal disk 16 through the thermoelectric material layer 30, and is solidified to become a thermoelectric material layer 32. Thereafter, step S14 is repeatedly performed until the dripping amount reaches a predetermined amount. One thermoelectric material layer is formed each time Step S14 is performed once.
[0026]
FIG. 4 shows a cross-sectional view of the thermoelectric material thus manufactured. On the surface of the water-cooled metal disk 16, a thermoelectric material layer 30, a thermoelectric material layer 32, a thermoelectric material layer 34, and a thermoelectric material layer 36 are formed. Each thermoelectric material layer is formed one layer each time Step S14 is performed once. Each thermoelectric material layer is an aggregate of columnar crystal grains extending in a direction perpendicular to the surface of the water-cooled metal disk 16, that is, in a direction in which the thermoelectric material layers are laminated, so that the thermal conductivity κ is low. Thus, the strength in the stacking direction is also increased. In addition, each thermoelectric material layer is directly manufactured by cooling the BiTe financial solution, so that it becomes a thermoelectric material with less impurities compared to a thermoelectric material manufactured by a method of cooling and then pulverizing and sintering. . Further, the average crystal grain size is 1 to 5 μm, and the filling rate is 98% to 100%. In this thermoelectric material, since the average crystal grain size is small, phonon scattering by the crystal grain boundary is increased and the thermal conductivity κ is reduced. Further, since the filling rate is high, the electrical conductivity σ is kept high.
[0027]
After forming a thermoelectric material by laminating a thermoelectric material layer on the surface of the water-cooled metal disk 16, the surface of the water-cooled metal disk 16 is cut off and the thermoelectric material is cut out (step S18). When the thermoelectric material is cut out in this way, it is cut out together with the water-cooled metal disk 16, so that it is not necessary to form an electrode on the thermoelectric material required in the subsequent element forming step. Therefore, the number of processes can be reduced.
[0028]
In the thermoelectric material manufacturing apparatus 100 of the present reference embodiment, to produce a thermoelectric material comprising a laminated structure by repeating the dropwise addition was cooled on a water-cooled metal disc 16 which rotates the BiTe alloy melt, laminated with other manufacturing devices Thermoelectric materials with a structure can also be produced.
[0029]
FIG. 5 is a schematic diagram of the configuration of the thermoelectric material manufacturing apparatus 200 of the present embodiment. The thermoelectric material manufacturing apparatus 200 replaces the water-cooled metal disk 16 of the thermoelectric material manufacturing apparatus 100 and can be moved in parallel to the center of the vacuum rod 18 by a drive shaft 50 provided on the right side facing the drawing, and the temperature-controlled circulation. The central portion of the vacuum rod 18 is cooled by a water cooled by water and kept at a constant temperature and the surface is covered with a BiTe compound liquid and a material having wettability, and a drive shaft 52 provided on the left side facing the drawing. And a cooling table 56 which is cooled by circulating water controlled in temperature and kept at a constant temperature and whose surface is covered with a BiTe compound liquid and a material having wettability, is opposed to the nozzle. The optical sensor 58 which can detect the dropping position of the BiTe combined financial liquid 22 dripped from 12 is provided.
[0030]
In the thermoelectric material manufacturing apparatus 200, the BiTe financial liquid 22 is dropped between the cooling table 54 and the cooling table 56 from the nozzle 12 in a state where the left and right cooling tables 54 and the cooling table 56 are separated from each other. When the BiTe financial solution 22 is detected by the optical sensor 58, the cooling table 54 and the cooling table 56 move, and the dropped BiTe financial solution 22 is sandwiched. The BiTe financial liquid 22 spreads in a thin film between the cooling table 54 and the cooling table 56 and solidifies. When the BiTe financial solution 22 is solidified, the cooling table 54 and the cooling table 56 are separated from each other. At this time, at least the cooling table 54 according to the adhesion between the surfaces of the BiTe financial solution 22, the cooling table 54, and the cooling table 56. And a thermoelectric material layer adheres to either of the cooling stands 56. That is, if the adhesion between the thermoelectric material layer and the surface of the cooling table 54 is very large compared with the adhesion between the surface of the cooling table 56, the thermoelectric material layer adheres to the cooling table 54, and the surface of the thermoelectric material layer and the cooling table 54 The thermoelectric material layer adheres to the cooling table 56 and the adhesion between the thermoelectric material layer and the surface of the cooling table 54 is less than the surface of the cooling table 56. The thermoelectric material layer adheres to both the cooling table 54 and the cooling table 56.
[0031]
After separating the cooling table 54 and the cooling table 56, the BiTe financial solution 22 is dropped between the cooling table 54 and the cooling table 56 from the nozzle 12. The cooling table 54 and the cooling table 56 sandwich the BiTe combined financial liquid 22 that has moved and dropped again, and deposit the BiTe combined financial liquid on the thermoelectric material layer that has previously been adhered. In this manner, the dropping of the BiTe financial liquid and the deposition on the thermoelectric material layer are repeated to produce the thermoelectric material having the laminated structure shown in FIG.
[0032]
Thus, also in the thermoelectric material manufacturing apparatus 200, a thermoelectric material provided with a laminated structure can be manufactured.
[0033]
The thermoelectric material of each embodiment uses Bi and Te as raw materials, but in addition thereto, an element selected from Sb, Ag, Pb, Ge, Cu, Sn, As, Se, Fe, Mn, Co, and Si It is also possible to include at least two types. In particular, a chalcogenite-based raw material of a combination of at least one of Bi, Sb, Ag, Pb, Ge, Cu, Sn, As and Se or Te, or a combination of any one of Fe, Mn, Co, Ge and Si Of these, silicide-based materials and BiSb-based materials are suitable.
[0034]
【The invention's effect】
As described above, in the thermoelectric material manufacturing method and thermoelectric material manufacturing apparatus of the present invention, the thermoelectric material in which at least two thermoelectric material layers of the first thermoelectric material layer and the second thermoelectric material layer are laminated is cooled. It can be formed on the surface of the table. As a result, it is not necessary to sinter into a bulk shape, and contamination of impurities into the thermoelectric material can be suppressed. Further, in the thermoelectric material of the present invention, each thermoelectric material layer is laminated, and each thermoelectric material layer has columnar crystal grains extending in the laminating direction, so that the thermal conductivity κ is low and the thermoelectric material has a high figure of merit. Can be manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a thermoelectric material manufacturing apparatus 100 of a reference embodiment.
2 is a diagram showing a manufacturing process of the thermoelectric material of the present reference embodiment.
3 is a cross-sectional view in the course manufacturing process of the thermoelectric material of the present reference embodiment.
FIG. 4 is a cross-sectional view of the thermoelectric material of the present embodiment.
FIG. 5 is a schematic view showing a configuration of a thermoelectric material manufacturing apparatus 200 of the present embodiment.
[Explanation of symbols]
10 Coils for high frequency heating, 12 nozzles, 14 heating container, 16 water-cooled metal disk, 22 BiTe financial liquid, 30, 32, 34, 36 thermoelectric material layer, 54, 56 cooling table.

Claims

A thermoelectric material manufacturing method for manufacturing a thermoelectric material by cooling a raw material melt,
A first thermoelectric material layer forming step of spreading the melt on a cooling table surface in a thin film shape and cooling the cooling table to form a first thermoelectric material layer;
The melt is spread on the first thermoelectric material layer in the form of a thin film and cooled by the cooling table via the first thermoelectric material layer to form a second thermoelectric material layer on the first thermoelectric material layer. A second thermoelectric material layer forming step;
With
In the first thermoelectric material layer forming step, the dropped melt is sandwiched between two cooling tables that are arranged opposite to each other and can be driven, and the melt is spread in a thin film on at least one surface of the cooling table and cooled. Then, separating the two cooling stands, forming the first thermoelectric material layer,
In the second thermoelectric material layer forming step, the dropped melt is sandwiched between the two cooling tables, and the melt is thinly formed on the first thermoelectric material layer formed on at least one surface of the cooling table. After cooling and spreading into a shape, separating the two cooling stands, forming the second thermoelectric material layer,
A method for producing a thermoelectric material, comprising producing a thermoelectric material having at least two laminated thermoelectric material layers on the cooling table.

A thermoelectric material production apparatus for producing a thermoelectric material by cooling a raw material melt,
Two cooling stands that are arranged opposite to each other and spread the melt on the surface in a thin film shape, and cooling,
Driving means for moving the two cooling tables to reduce the distance between the two cooling tables;
A melt supply means for supplying the melt between the two cooling tables ;
With
The driving means includes an interval for sandwiching the melt supplied by the melt supply means, and then the melt is spread and cooled in a thin film shape between the two cooling stands so that the first thermoelectric material layer is formed. After being formed, the two cooling tables are driven to have a distance apart, and according to the adhesion between the surface of the two cooling tables and the first thermoelectric material layer, at least one of the cooling tables Drive to form a first thermoelectric material layer on the surface,
Further, the driving means drives in a direction to reduce the interval between the two cooling stands so as to sandwich the melt supplied by the melt supply means, and then the first cooling means is placed on the surface of at least one cooling stand. After the melt is spread in a thin film between the two cooling stands on which the thermoelectric material layer is formed and cooled to form a second thermoelectric material layer, the distance between the two cooling stands is increased. Driving, and driving to form a second thermoelectric material layer on the first thermoelectric material layer formed on at least one surface of the two cooling stands,
A thermoelectric material manufacturing apparatus for manufacturing a thermoelectric material having a thermoelectric material layer having at least two layers laminated on the surface of the cooling table.